Production of diolefins



Patented Jan. 4, 1949 1 2,458,082 PRODUCTION OF DIOLEFINS Myron 0. Kilpatrick, Bartlesville, Okla., assignir to Phillips Petroleum Company, a corporation of Delaware Application August 6, 1946, serial No. 688,623

10 Claims. l

This invention relates to the dehydrogenation of hydrocarbons for the manufacture of diolefins. In one of its more specific aspects, the present invention relates to the dehydrogenation of hydrocarbons containing four and iive carbon atoms per molecule simultaneously to produce a mixture of butadiene and isoprene.

It is known that diolens may be produced by the cracking or dehydrogenation of hydrocarbons.

Butadiene may be prepared by the dehydrogenation of butane and butylenes; pentadiene and isoprene by the dehydrogenation of perltane and amylenes. Various amounts of the four and five carbon atom diolens may also be obtained by the cracking of petroleum, Butadiene and related diolefins have been found in numerous instances among the products of low pressure pyrolysis of various hydrocarbons, including both parailns and olens. In general, the diolen yields obtained by simple pyrolysis are loW. On the other hand, the dehydrogenation of parailins and oleflns with the use of contact type dehydrogenan tion catalysts results in much higher yields of diolefms. The yields of dolefins are improved in some instances by dehydrogenation at low pressure or in the presence of diluentssuch as steam,`flue gas, methane, and the like. The present invention is concerned with the catalytic dehydrogenation of paraiiins and olens to produce diolens, and particularly with the simultaneous dehydrogenation of four and ve carbon atom parains and oleiins to produce a mixture of four and five carbon atom diolens.

Diolens, especially 1.3-butadiene, 1.3-pentadiene, and isoprene (2-methyl1.3butadiene) are valuable as monomers in the polymerization processes for the production of synthetic rubbers. Synthetic rubbers may be produced from diolelns individually or in admixture with other polymerizable organic monomers; The most widely used synthetic rubber at the present time is GRf-S, a product produced by copolymerization of Lil-butadiene and styrene. Similar copolymers of 1.3-pentadiene and isoprene are produced and are especially suited to some uses. The choice of the diolen used in the manufacture of synthetic rubberdepends to a` large extent upon the use to which the resulting product is to be put. Hence both the four and five carbon atom diolens are valuable as starting materials for the `pro- Y of LES-butadiene While n-pentane and amylenes are used to produce pentadiene and isoprene. It has been proposed to produce butadiene by the catalytic treatment of the l butene-con'taining hydrocarbon mixture resulting from the dehydrogenation of normal butane. However, so far as I am aware, the use of a mixture of pentane or amylene with butylene and simultaneous dehydrogenation of the mixture to produce mixed diolenes has not been heretofore carried out. By the process of the present invention itis possible to obtain good yields of both 1.3% butadiene and isoprene in a single operation. My process is used to produce an eiTluent containing the mixed diolerlns from which substantially pure butadiene and isoprene may be separately recovered. My invention provides for the economical production of butadiene by catalytic dehydrogenation and also includes the production of substantial amounts of isoprene or pentadiene in the same dehydrogenaton step with little, if any, effect on the butadiene capacity.

An object of this invention is to provide an improved process for the production of diolefins. Anotherobject is to provide aprocess for the dehydrogenation of four and ve carbon atom hydrocarbons simultaneously to produce a mixture of iour and iive carbon atom diolens, Still another object is to provide a process wherein commercial quantities of isoprene may be produced incidentally to the production of butadiene. Other objects and advantages will be apparent to those skilled in the art from the following detailed description.

The accompanying drawing is the diagrammatic flow sheet illustrating the various steps in the production and recovery of diolens by the process of the present invention.

At the present time butadiene is produced in large quantities by the catalytic dehydrogenation of n-butylenes; Either 1butene, 2butenes, or a mixture of the n-butylenes, may be used for catalytic dehydrogenation to butadiene. In carrying out the dehydrogenation, butylenes are generally admixed With steam in proportion within the range of from about 3 `to 10 volumes of steam per volume of butylene. In general, the pressure is kept within the range of from about atmospheric to about 50 pounds per square inch gage. `Low pressures` are favorable to the dehydrogenation reactionj pressures below atmospheric pressure result in increased conversion to the desired dioleijin. From a practicalstandpoint, however, it is desirable..to.use pressures at least as high as atmospheric pressure to prevent leakage of air into the system. In most operations, the pressure at the inlet to the catalyst zone is at least sufficiently above atmospheric pressure to cause ow through the zone at the desired rate with a pressure somewhere in the neighborhood of atmospheric pressure at the outlet of the -catalyst zone. Partial pressures of less than atmospheric pressure and desirably below 0.5 atmospheres may be maintained within the catalyst chamber by dilution with steam or other inert diluent in suflcient volume.

Other diluent gases which may be used comprise the hydrocarbons more,1 refractory than the four carbon atom hydrocarbons, particularlyv methane and propane, and other inert gases,y

especially carbon dioxide, hydrogen and nitrogen. Generally, Water vapor or steam is the preferred diluent due to its availability and beneiicial effect in the dehydrogenation reaction, While hydrogen may be used, the presence of any considerable amount of it when the partial pressure of the olefins is also low adversely affects the equilibrium in the olein-diolen conversion.

Space velocities of from about 500 to about 5000 volumes of feed per volume of catalyst per hour may be used. Space velocities Within the range of from about 700 to about 1500 volumes of feed per volume of catalyst per hour are preferred.

By the process of the present invention the C5 diolefins, and in particular isoprene, are produced simultaneously with the production of butadiene by dehydrogenation. By this process the production of butadiene from butylenes is substantially unaffected While substantial quantities of five carbon atom diolens are simultaneously prof..

duced. A part of the five carbon atom olefin is converted to butadiene, thus supplementing the yield of butadiene from butylenes. The advantages of the process Will be readily apparent to those skilled in the art.

According to the present invention a feed stream is made up comprising a ve carbon atom hydrocarbon more saturated than the diolen, e. g., pentane or an amylene. Pentane or the various amylenes individually or in admixture with one another may be used in the process of this invention.v From about 5 to about 20 volumes of the five carbon atom hydrocarbons are used with from about "I0 to about 95 volumes of butylene. Of the Various amylenes, Z-pentanes and trimethylethylene (2-methyl-2-butene) are preferred. Trimethylethylene is preferred for the production of isoprene and is converted to isoprene with very little production of other dioleins. Pentene-Z yields a mixture of butadiene and ve carbon atom dioleiins. The dehydrogenation of 2-pentenes yields mainly 1,3-butadiene, some 1,3-pentadiene (piperylene) `and perhaps some isoprene. Trimethylvethylene yields mainly isoprene, some butadiene, and occasionally some piperylene. The overall yield of diolens based on 2-pentenes or trimethylethylene charged to the dehydrogenamay be as high as from about 35% to about A typical refinery C5 fraction has approximately the following composition: l-pentene, 9%; 2- pentenes, 17%,; trimethylethylene, 9%; unsymmetrical methylethylethylene (2-methyl-1-butene), 5%; and the remainder predominantly pentane. Such a mixture may be used as the C5 feed for admixture with butylenes in the process of the present invention. The amylenes may be separated from the refinery fraction by solvent extraction with a polar solvent capable of exerting a preferential solvent action upon olens as Til distinguished from parafns and upon the desirable higher-boiling amylenes Z-pentenes and trimethylethylene as distinguished from the less desirable low-boiling amylenes (l-pentene and unsymmetrical amylene) Catalytic isomerization may be employed to increase the concentration of Z-pentenes and also trimethylethylene in the C5 stream. This step converts 1 -pentene largely to Z-pentenes and also converts unsymmetrical amylene to trimethylethylene. Thus ccncentration of the desirable higher-boiling amylenes is increased at the expense of the less desirable low-boiling amylenes. This isomerization is Well known in the art and forms no part of the present invention.

A specific modification of the invention is illustrated in the accompanying ligure wherein a hydrocarbon feed stream comprising 80 to 90 per cent butylenes and from 5 to 10 per cent five carbon atom hydrocarbons, such as a concentrated mixture of 2-pentenes and trimethylethylene, enters the system through pipe I and passes through a preheating furnace 2 into the catalyst chamber 3. In the pre-heater 2 the feed is heated to approximately the desired conversion temperature, preferably to a temperature within the range of from about 1100 to about 1200 F. Steam or other stable gaseous diluent enter the system through pipe 4 and may be passed via line E to the feed stream entering furnace 2 or it may pass from pipe 4 to a separate furnace 'l and thence through pipe t to the inlet of the catalyst chamber 3. 1n the furnace l the diluent is heated to a temperature a least as high as the conversion temperature.

In some instances it is desirable to heat the diluent to a temperature somewhat above the conversion temperature such thatl admixture of the preheated diluent and preheated feed stock prior to introduction to the catalyst case results in a mixture of feed and diluentl having the desired conversion temperature. This latter method of operation is sometimes advantageous in that it results in quickly vheating the feed from a temperature below that at which non-'catalytic conversion begins to the conversion temperature immediately prior to introduction to catalyst zone. While a partial uncatalyzed conversion is permissible and even sometimes desirable with low steam to hydrocarbon ratios, the efliciency of the conversion to desired products is improved by rapidly preheating the feed stream and introducing it into the catalyst Zone before substantial conversion occurs. The dehydrogenation is carried out by passing the preheated reactants in ad- Inixture with the diluent over a catalyst in the zone 3. The dehydrogenation zone may conveniently be in the form an insulated vessel containing aYlarge bed of dehydrogenation catalyst in granular or pellet, form supported by a suitable means such as a perforated plate O1' Series of perforated plates vertically spaced through the catalyst bed. The catalyst, Which is more fully discussed hereinafter, may also but less desirably be disposed in tubes of small diameter with provision for heat transfer to the catalyst and reactants-through the wall of the tube by heat exchange with hot gases. Effective dehydrogenation catalysts and arrangements of apparatus are well known in the art and need little, if any, discussion inthe present disclosure.

From the catalyst cases the dehydrogenation effluent passesto a cooler 9.where it is cooled to a temperature below that at which conversion, decomposition or other undesirable reactions take place. Water vapor is condensed, the condensate separated from the gaseous eluent in separator II,` and withdrawn through line I2, the dehydrogenation effluent is then compressed in the compression system I3 to a pressure of about 200 pounds per square inch and cooled by cooler I4 to substantially atmospheric temperature. Compression and cooling of the effluent gases causes some condensation. The condensed portion of the efiluent is separated from the vaporous portion in accumulator I6. Vapors from accumulator I6 are passed to a mineral seal oil absorber I1 operated to effect recovery of substantially all four carbon atom and heavier hydrocarbons from the gas. Propane and lighter hydrocarbons are unabsorbed and pass via line I8 out of the system for use as fuel in the plant. Rich oil, that is, mineral seal oil containing absorbed C4 and heavier hydrocarbons, passes from absorber II via line I9 to a mineral seal oil stripper 2| wherein the absorbed hydrocarbons are released from the absorption oil. Lean absorption oil passes from the stripper to the absorber via line 23.

VCondensate from accumulator `Iii is passed through line 24 to a depropanizer` 26. Recovered C4 and heavier hydrocarbons from stripper 2| are passed through line 22 to the depropanizer in admixture with the condensate from the accumulator. In the depropanizer 26, which is a fractional distillation column, any residual propane and lighter hydrocarbons` are eliminated from the dioleiin-containingstream. The light hydrocarbons are taken overhead from the depropanizer through line2l for use as fuel or for 'other purposes. `Butanetand higher-boiling hydrocarbons are withdrawnfrom the base of the depropanizer and passed via line 28 to the butene- 2 column 29. l i i The effluent from the dehydrogenation step comprises a mixture of hydrogen,`propane and lighter hydrocarbons, normal butane, normal pentane lbutene,` Z-butenes (cis and trans), butadiene, 1-pentene, 2-pentenes, unsymmetrical amylene, trimethylethylene, pentadene, isoprene and small amounts of higher boiling hydrocarbons. The boiling points of the various four and five carbon atom hydrocarbons are as follows:

Compon en t 1,13%? l?? I-Butcne 2l 1,'3-Butadiene 24 trans-Z-Butene 34 cis-Z-Butcnc. 39 l-lviethyl-bliutene 68 f l-Pentene s6 2Methyl-l Buren@ 88 2 Methyl Butadlcn 93 trans-Z-Pentenc 97 cs-2Peutene.. 99 2-Methyl-2-butcne (trimetliylethylcnc). 101 1,3APentz-:diene (piporylene) 10S drocarbons from the Z-butene column pass via line 3l to a solvent extraction unit 32. In unit 32 a separation is made by a selective solvent between the butylenes and the butadiene. Butadiene is selectively absorbed while the butylenes, which `are unabsorbed, are taken overhead and recycled through line 33 to the feed stream entering through line I. The solvent passes from the absorber 32 through line 34 to a stripper 36 where the butadiene is separated from the solvent, and the solvent is returned to the absorber 32 through line 31. The butadiene thus substantiallyV freed from butylenesis withdrawn through line 38 to fractionator 39; Substantially pure butadiene is taken from fractionator 3S through line 4I as product. The higher boiling hydrocarbon fraction from the butene-Z column 29, comprising removed cis-2-butene is removed through line 42 and admixed with any Z-butenes or higher-boiling hydrocarbons withdrawn from the base of fractionator 39` through line 43 and this mixture is passed to a fractional distillation column 44 known as a debutenizer.

In the debutenizer 44, Z-butenes and lower boiling hydrocarbons are separated from the C5 and heavier hydrocarbons and withdrawn through line 46 for `recycling to the feed stream entering the system through line I. The C5 and heavier hydrocarbons are passed through line 47 to a fractional distillation column 48 wherein the Cs and heavier hydrocarbons are separated from the C5 stream.` The Ce and heavier hydrocarbons are removed from the fractionator through line 49. The C5 stream is passed through line 5| to an extractor 52`Wherein a separation is made by a selective solvent between the ve carbon atom diolens and the less unsaturated C5 hydrocare bons. *The amylenes, which are not dissolved, pass through line 53 and are recycled together with the butylene from line 4B to the feed stream. Thesolvent passes from the absorber 52t-hrough line 54 to stripper 56 where the diolens are separated, and the solvent is returned to absorber 52 through line `5'1. The `dioleiin mixture thus substantially freed of amylenes and other less unsaturated hydrocarbons is taken through line 58 to fractionation system 59 for final separation. Any hydrocarbons higher boiling than the desired diolefins are withdrawn from the fractionation system 59 through line GI. The ve carbon atom diolens are taken from the fractionation system through line 62 and `may be subjected to further purification steps to separate isoprene and if desired, 1,3-pentadiene, from other less desirable diolens. i

Various modification-s of the process illustrated in the figure will be obvious from my disclosure and no attempt will be made to discuss all of the possibilities within the scope of my invention. For example, the separation of C3 and lighter material from theefliuent of the dehydrogenatioh step may be performed in a single fractionation or with-other auxiliary operations such `as refrigeration and the like. Also other methods for separating butadiene and-isoprene from the de hydrogenation effluent may be utilized without departing from the spirit of the present invention. Itwill be evident also that the selective absorption steps might be combined to recover a mixture of butadiene and the ve carbon atom diolefins which may then be subsequently sepa rated by any of various methods.

`It will be obvious to one skilled in the art that the accompanying flow diagram illustrative only and that valves, condensers, fractionation reflux lines and other auxiliary equipment have been omitted for the sakeof simplication. It is believed, however, that the figure clearly illus trates the various process steps of this` specific modification` of my invention and that thegure taken together with theaccompanying description. Williclearly` explain this modification to those skilled in theart.

In the operation of the dehydrogenation step they charge stock is, prepared in such proportions thatl partial pressure of oleiinsI is less than one atmosphere andfpref-erably in the range of 0.2 to 0.5 atmosphere. The other constituents of the mixture are principally parailins and steam together withl anyr Cs hydrocarbons or, oth-er diluent whichmayfbe added.

The eilluent of the catalytic dehydrogenation step-is cooled to condense and separate water and any-high boiling polymer or tar. The method of cooling may be designedv to provide an extremely rapid reductiony of temperature, such as the introduction of water or other quenching mediums. After separation of the condensate the hydrocarbon vapors are compressed, cooled and processed to remove hydrocarbons higher and lower boiling than the desired C4 and Cs hydrocarbons in a series of separational steps,

In the process of this invention the eiuent vapors from the dehydrogenation step are processed to separate any high boiling material formed` by the catalytic treatment, and to remove prop-ane and lower boiling gaseous by-products. The separation of light gases is indicated in two stages, that is, separation of the gases from the condensate in accumulator I5 followed by a vapor recovery system to recover C4 and heavier hydrocarbons from the light gases, and fractional distillation in depropanizer 26 to eect removal of propane and lighter hydrocarbons` retained in the condensate in accumulator I6 or absorbed by thel mineral seal oil absorber l'l. Hydrogen-containing gas from either the mineral seal oil'absor-berv or the depropanizer may be returned to the feed stock ahead of the catalyst if desired. Precautions should be observed in such an operation to avoid building up concentrations of hydrogen to the point where the dehydrogenation reaction is suppressed.

The, stream taken overhead' through line 21 from the depropanizer 26 contains a relatively high percentage of propylene. If desired, a part of the stream fromv the depropanizer may be recycled to the dehydrcgenation step as a part of the diluent gases used therein. The propylene is a potential hydrogen acceptor capable of prometingl the dehydrogenation reaction. At least a. portion of the C3 hydrocarbons must be removed from thesystem toprevent pyramiding an excessivel recirculation of this relatively insert material which increases the compression requirement of the process. In any event substantially complete separation of propane is desirable prior tov the diolelin purification steps indicated in the process.

The recovery of the diolefns` from the resulting unsaturated hydrocarbon mixture may be .eifected by the method illustrated or by other known processes which produce substantially equivalent results. Solvent extraction,` azeotropic distillation and chemical processes such as the formation of a complex, for example, sulfones 'or cuprous salt complexes, are known to be effective methods. for use` in the separation and purification ofv dioleiins.

The catalysts used in the dehydrogenaticn step are those of satisfactory activity in promoting selective olefin dehydrogenation at temperatures within the. range of 1100 to.1 4.00 F. and inthe presence of Water vapor. Those catalysts which are particularly suited' tothe process of the present invention are catalysts comprising a mixture of metal oxides. Promoters of thewat-er gas. reaction mayl be advantageously included in the catalyst composition. Catalysts which have been found' particularly effective foruse in theprocess off this invention are those prepared by treatment of bauxite or alumina with the oxide or hydroxide of barium or strontium insuch a manner that the,` adsorbentmetal oxide carrier is impregnated with the metal compound. The oxides of aluminum i and magnesium have been found toV give especially satisfactory catalysts as have also those of zirconium and titanium. Both synthetic-preparations cf the substantially pure oxides, hydrated oxides, or hydroxides, and also` natural mineral ores comprising those oxides yield satisfactory catalysts. High porosity or specific surface and other qualifications of good catalysts are desirable in these materials. Other `catalysts which have been found particularly suited to the practice of the presents invention are those of approximately the following` composition:

Per cent by Weight Iron oxide A 93 Chromium oxide 5 Potassium hydroxide 2 and Per cent by Weight Aluminum oxide 89 Barium oxide 5 Magnesium oxide 3 Potassium hydroxide 3 Catalysts may be prepared by impregnating pellets, granules, or particles of the latter irrsoluble metal; oxide carrier material, e. g. aluminumv oxide, iron oxide and the like, with an aqueous solution of the soluble components folloWed` by evaporation of Water. The catalysts specifically mentioned above may be preparedv in this manner. These catalysts do not lose activity to any appreciable extent in contact with steam at elevated temperatures. The catalysts mentioned are selective to dehydrogenation and cause very little cracking or polymerization reactions to take place.; It ifs to be understood, however, that` other catalysts of satisfactory activity in promoting selective olen dehydrogenation in the presence of water vapor at temperatures within the range of 1100 to 1400 F, may be employed in the present process.

Steam is particularly desired as a diluent .in conjunction with Water resistant catalysts, i. e., those which maintain high activity in the presence of steam, in that the water vapor reduces the deposition of tar or carbon on the catalyst during the conversion period. Water resistant catalysts of the typ-e described hereinabove result in prolonged period of maximum catalyst activity and greatly reduce time requirements for reacti vation.

The following specic example illustrates a specific application of my process without implying any unnecessary limitations thereto.

A four carbon atom feed stream containing approximately 95 per cent butenes by volume is admixed with a five carbon atom feed stream containing approximately per cent amylenes by volume and with steam. The mixture is preheated to the desired dehydrogenation temperature and passed over a catalyst comprising aluminia admixed with about 5 weight per cent barium hydroxide to produce diolens. The steam is preheated and admixed with the hydrocarbon feed stream just prior to contact of the catalyst. Operating conditions are within the range indicated below:

Composition of hydrocarbon feed: Per cent by Vol.

Butylenes 80-90 C(Amylenes) 5-10 Butane 5-10 Steamehydrocarbon ratio 8 1-15 1 Temperature of the catalyst cases 10001300 F. Pressure of the catalyst cases 20-30 psia A mixture comprising approximately 65 per cent Z-pentenes and 35 per cent trimethylethylene is used as the amylene feed in this example. The eiiiuent from the catalyst cases is cooled, compressed and processed for the removal of C3 and lighter hydrocarbons and Cs and heavier hydrocarbons as indicated in the accompanying flow diagram. A fractionation is made between trans-Z-butene and lower boiling C4 hydrocarbons and cis-Z-butene and C5 hydrocarbons. Butadiene is separated from the C4 stream and the live carbon atom dioleins are separated from the C5 stream by extractive distillation with furfural. The butadiene yield is about 55 weight per cent based on the butylenes reacted and the isoprene yield is about 45 weight per cent based on trimethylethylene reacted. Unconverted C4 and C5 olens and parains are recycled to the dehydrogenation step. Yields are expressed as weight per cent (ultimate yields) based on the hydrocarbon reacted. The yield of isoprene is at a maximum when substantially pure trimethylethylene is used as the C5 in the feed stream. When 2-pentenes are used as the Cs in the feed stream the butadiene yield is increased approximately 3 per cent based on the butyl-enes reacted due to the fact that Z-pentenes yield 1,3-butadiene in amount equivalent to about 30 weight per cent of the Z-pentenes reacted. The yield of rive carbon atom diolefins from 2-pentenes, the yield amounting to about per cent by weight based on the Z-pentenes reacted is correspondingly reduced.

Since the present invention may be practiced otherwise than as specifically described herein and since various modications and variations of the process will be apparent to those skilled in the art, the foregoing descriptive matter should be construed as illustrative only and not as limiting to the invention.

I claim:

l. A process for the production of dioleins which comprises contacting a mixture of butenes and about 5 to about 10 volume per cent of 5 carbon atom hydrocarbons more saturated than diolens at a temperature within the range of from about 1000 to about 1300 F. with a dehydrogenation catalyst in the presence of from about 8 to about 15 volumes of steam per volume of hydrocarbon.

2. A process for the production of diolefins which comprises passing butene in admixture with from about 5 to about 10 volume per cent of a C5 hydrocarbon more saturated than a dioleiin into contact with a dehydrogenation catalyst at a temperature within the range of from about 1000 to about 1300 F. in the presence of from about 8 to about 15 volumes of steam per volum-e of hydrocarbon mixture.

3. A process for the production of diolens which comprises passing butene in admixture with from about 5 to about 10 Volume per cent of pentene into contact with a dehydrogenation 10 catalyst at a temperature Within the :range of from about 1000 to about 1300 F. in the presence of from about 8 to about 15 volumes of steam per Volume of hydrocarbon mixture.

4. A process for the production of dioleiins which comprises passing a mixture of butene and Z-pentene into Contact with a dehydrogenation catalyst `at a temperature within the range of from about 1000 to about 1300 F. in the presence of from about 8 to about 15 volumes of steam per volume of hydrocarbon mixture.

5. A process for the production of diolefns which comprises passing a mixture of butene and trimethylethylene into contact with a dehydrogenation catalyst at a temperature within the range of from about 1000 to about 1300 F. in the presence of from about 8 to about 15 volumes of steam per Volume of hydrocarbon mixture.

6. A process for the production of diolens which comprises admixing butene with pentene in the ratio of about to 90 parts by volume of butene to 5 to 10 parts by volume of pentene, admixing the resulting mixture with steam in an amount equivalent to from about 8 to about 15 volumes of steam per Volume of hydrocarbon mixture and passing the steam-hydrocarbon mixture into contact with a dehydrogenation catalyst at a temperature within the range of from about 1000 to about 1300D and at a pressure within the range of from about 0 to about 100 pounds per square inch gage.

7. A process for the production of dliolens which comprises admixing butene with pentene in the ratio of about 80 to 90 parts by volume of butene to 5 to 10 parts by volume of pentene, admixing the resulting mixture with steam in an amoimt equivalent to from about 8 to about 15 volumes of steam per volume of hydrocarbon mixture and passing the steam-hydrocarbon mixture into contact with a dehydrogenation catalyst comprising a mixture of metal oxides at a temperature within the range of from. about 1000 to about 1300 Fand at a pressure within the range of from about 0 to about 100 pounds per square inch gage.

8. A process for the production of diolefins which comprises admixing butene with Z-pentene in the ratioof about 80 to 90 parts by Volume of butene to 5 to 10 parts by volume of 2-pentene, admixing the resulting mixture with steam in an amount equivalent to from about 8 to about 15 volumes of steam per volume of hydrocarbon mixture and passing the steam-hydrocarbon mixture into contact with a dehydrogenation catalyst comprising a mixture of metal oxides at a temperature within the range of from about 1000 to about l300 F. and at a pressure within the range of from about 0 to about 100 pounds per square inch gage.

9. A process for the production of diolens which comprises admixing butene with trimethylethylene in the ratio of about 80 to 90 parts by volume of butene to 5 to 10 parts by volume of trimethylethylene, admixing the resulting mixture with steam in an amount equivalent to from about 8 to about 15 volumes of Ksteam per Volume of hydrocarbon mixture and passing the steammydrocarbon mixture into contact with a dehydrogenation catalyst comprising a mixture of metal oxides at a temperature within the range of from about 1000 to about 1300 F. and at a pressure within the range of from about 0 to about pounds per square inch gage.

10. A process for the production of mixed C4 and C5 diolefins which comprises contacting a :11 A12 mixture of a plurality of-C4hydrocarbonsincludu ing a substantial amount of vurlsaturates and REFERENCES CITED about 5 to about l'volume per cent 'of a plurality The following references are of record in the of C5 hydrocarbons including a substantial @e of `this atent. amount of unsaturates at a temperature Within 5 l' p the range of labout 1000 to about 1300 F. with a UNITED STATES PATENTS suitable dehydrogenaton catalyst in the presence o1 from about 8 Vto about 15 Volumes of steam per Number Name Date volume of hydrocarbon mixture under conditions 2,335,484 Wright sept. 25, 1945 of time and pressure which produce C4 and C5 10 diolefns.

MYRON O. KILPATRICK. 

